CBSVs have slightly flexuous particles with a modal length of ca 650 nm. Particles contain single-stranded genomic RNA of approximately 9008-9070 nt which is encapsidated in a coat protein of ca 43 kDa for UCBSV and ca 45 kDa for CBSV (Winter et al., 2010). The genome structure of the cassava brown streak viruses is unique because of a MAf/Ham1-like sequence inserted upstream the coat protein gene and a P1 gene to which gene silencing suppression function was assigned.
Related crop
- Manihot esculenta
Related invasive species
- Cassava mosaic disease
Related Farm Practice
- Suppression
- Development
- Diagnosis
The name brown streak was given to the disease from the brown lesions which sometimes appear on young green stems. These were the first symptoms of the disease to be recognised, however stem lesions are not the most characteristic symptom of infection and occur only infrequently.;Unlike symptoms induced by the majority of plant viruses, those of CBSD in cassava normally affect mature or nearly mature leaves but not expanding, immature leaves. They consist of a characteristic yellow or necrotic vein banding which may enlarge and coalesce to form comparatively large, yellow patches. Tuberous root symptoms may also be present: these consist of dark-brown necrotic areas within the tuber and reduction in root size, lesions in roots can result in post-harvest spoilage of the crop. Leaf and/or stem symptoms can occur without the development of tuber symptoms, thus, of plants with above-ground symptoms surveyed in southern Tanzania, 21% failed to develop root necrosis (Hillocks et al., 1996).;The symptoms of the disease vary greatly with variety and environmental conditions, making diagnosis difficult, particularly when plants are infected both with CBSD and cassava mosaic disease.